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Message
Ed said:
John, I don't know the current draw,
but I would strongly suggest that you replace fuses in critical circuits like
ignition with quality circuit breakers. Fuses are OK and have their place
and I used them in my aircraft but, in my opinion they do NOT belong
in a critical circuit. I have never reset a fuse, but I have reset circuit
breakers that popped due to a temporary overload and got the system back in
operation. FWIW
Ed,
As always I appreciate you're input.
As you probably know, this is an age old discussion which has been played out ad
nausium by people far more qualified than I. Bob Nuckolls had a very
comprehensive paper on the subject on his web site http://aeroelectric.com
I think the logic goes something
like this:
1. It is better to plan for a failure
and be able to complete the flight without the offending item, than it is to try
to ensure that the item never fails. It WILL fail sometime. Take a look at his
product "guarantee".
2. If a circuit breaker pops, either
you have a bad breaker, or there's a reason for the overload. Resetting it in
the second case is a bad thing, since you could now be overloading the
wire. If it had been a fuse, then you wouldn't have had to reset it in the
first case.
3. If a fuse blows, or a breaker pops,
then the right thing to do (according to Bob) is to continue with you're backup
plan and fix the problem on the ground. In this case that meant run home on
trailing coils only. (not that I knew this at the
time)
Of course, many old and bold flyers
have stories of saved bacon from resetting breakers. We've all heard them,
and I believe them. Bob would [and does] argue that these incidents were
mostly bad breaker incidents, and there should have been a backup plan that
didn't involve resetting the breaker. Given this argument, a fuse is more
reliable.
In my case, maybe the coils take 7 or
8 amps each. I'd designed the circuit for one coil, forgetting that there was
double the draw because there were 2 coils on each circuit. So, perhaps I was in
danger of seriously overloading the wire. Had I reset a breaker maybe I'd
have had a fire to deal with instead of just a rough engine. Not a bad
example of Bob's point.
Understand, I'm not so much arguing
for one side or the other, as I am making sure that both sides are presented. I
chose to follow Bob's logic. However - trying to cover my back (in case he was
wrong) my fuses are within reach during flight, and I have spares lined up
on the back of the fuse panel. :)
Regards,
John
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